In existing applications, microstrip propagation can be converted to waveguide propagation over the same mechanical part. The transition is provided by a printed-circuit board, of which a part outside of the waveguide is a microstrip line, whereas the part inside the waveguide is an inserted probe. However, hermeticity cannot be acquired unless a hermetic window is used at the opening of the waveguide because the transition between microstrip and waveguide propagations takes place on the same mechanical part. On the other hand, appending the hermetic window increases both complexity and cost of the structure.
In another application of the known technique, an adaption of the transition method between coaxial and waveguide propagations is stated. The coaxial connector of the structure and the microwave module are linked via a cabling component, hence, the transition between microstrip and waveguide propagations is achieved in a roundabout way. Despite the hermeticity that is attained at the module side, a degradation at the overall performance is inevitable because of the cabling component holding the connection between the transition structure and the microwave module. The cabling component causes an increment in a noise factor of the system when placed at the input of the microwave module, whereas a decrement in amplitude of the output power occurs when the cabling component is placed at the output.
In a known technique, a waveguide to microstrip transition module is mentioned in a United States patent document U.S. Pat. No. 5,202,648 (A). This module transmits electromagnetic energy received between the waveguide and the signal processing circuit. The module consists of a waveguide, a circuit panel and a microstrip line. The microstrip line directed by the waveguide is linked to the signal processing circuit. The system is covered hermetically to surround the circuit panel.
In another known technique, a waveguide system including a tuning element, an adaptor, a waveguide and pin link elements is mentioned in a United States patent document U.S. Pat. No. 6,549,106 (B2).